1 Field of the Invention:
The present invention relates to a steering apparatus for steering a motor vehicle, the steering apparatus being capable of varying the ratio (steering angle ratio) of a steered angle of a steerable road wheel to a steering angle of a steering wheel.
2 Description of the Relevant Art:
One conventional steering apparatus with a variable steering angle ratio for a motor vehicle having steerable road wheels, is disclosed in Japanese Laid-Open Patent Publication No. 61-122075, for example. The disclosed steering apparatus comprises a planetary gear mechanism disposed in a steering force transmitting path between a steering wheel and a steering gear mechanism. The planetary gear mechanism has a sun gear coupled to the steering wheel, a ring gear coupled to the steering gear mechanism, and a carrier coupled to a motor. The carrier is driven by the motor depending on the speed of travel of the motor vehicle for adjusting the steering angle ratio.
In the conventional steering apparatus with the variable steering angle ratio, the sun gear, the carrier, and the ring gear of the planetary gear mechanism are rotatable independently of each other. Therefore, it is difficult to align the neutral position of the steering wheel with the neutral position of the steerable road wheels.
Another problem of the conventional steering apparatus with the variable steering angle ratio is that the motor operates for a long period of time and consumes a large amount of electric energy because the motor is energized each time the steering wheel is turned.
The present invention has been made in an effort to solve the above problems of the conventional steering apparatus with the variable steering angle ratio.